The answer is simple:
0: Copy UserActivityHook.cs to your project, add an instance of the UserActivityHook object, set up the event handlers, enter Debug mode, and waste a couple of hours trying to fix the Win32Exceptions thrown on lines 538 and 562 before coming back to this site and seeing this solution.
1: Go to the project properties page (right-click the project name and select properties)
2: Go to the Debug tab and uncheck "Enable the Visual Studios hosting process"
3: Realize that the ctrl and alt keys map to Keys.LControlKey, Keys.RControlKey, Keys.LMenu, and Keys.RMenu, since you're now able to see the results of each of your key presses. (It really makes a lot more sense, now that I can see how Windows is managing each of the keys... Just wasn't obvious before.)